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238056 results in Physics and Astronomy

Page 215 of 11903

  • 4 - Multimode instabilities: Linear and nonlinear regimes

  • from Part 1 - Fundamentals
  • Ye Zhou, Lawrence Livermore National Laboratory, California
  • Book:
    Hydrodynamic Instabilities and Turbulence
    Published online:
    27 June 2024
    Print publication:
    19 December 2024, pp 66-90

  • Summary

    The multi-mode instability is the simultaneous growth across many wavelengths. This is closer to the reality of many applications. We provide a detailed treatment of the various stages of development. It is widely believed that many turbulent flows, such as RTI, RMI, and KHI mixing layers, evolve toward self-similarity. Here, the RTI grows quadratically with time, and the suitable proportionality constant is the subject of ongoing research. The growth exponent for RMI is also the subject of ongoing research. I also discuss measurements of these parameters in experiments and simulations arising from multimodal initial perturbations.

  • 1 - A first glimpse of Rayleigh–Taylor, Richtmyer–Meshkov, and Kelvin–Helmholtz instabilities

  • from Part 1 - Fundamentals
  • Ye Zhou, Lawrence Livermore National Laboratory, California
  • Book:
    Hydrodynamic Instabilities and Turbulence
    Published online:
    27 June 2024
    Print publication:
    19 December 2024, pp 3-15
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  • Summary

    I will describe the earlier efforts in both hydrodynamic instability and turbulence mixing research and provide a broad non-mathematical overview of the significance of turbulence mixing on scientific and engineering applications. I will briefly explain several varied applications in which hydrodynamic instability plays a critical role, namely, inertial confinement fusion (ICF), supernova explosions, solar prominences, paintings, and combustions and detonations, among others, to provide the reader with an idea of what will be discussed later in the book.

  • Impulse-driven release of gas-encapsulated drops

  • Guillaume T. Bokman, Luc Biasiori-Poulanges, Bratislav Lukić, Kevin Schmidmayer, Claire Bourquard, Enea Baumann, Alexander Rack, Britton J. Olson, Outi Supponen
  • Journal:
    Journal of Fluid Mechanics / Volume 1001 / 25 December 2024
    Published online by Cambridge University Press:
    19 December 2024, A51
    • Article
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      • Open access
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  • Gas-encapsulated drops, much like antibubbles, are drops enclosed in a bubble within a liquid. They show potential as payload carriers in fluid transport and mixing techniques where sound waves can be leveraged to induce the collapse of the gas core and the subsequent release of the drop. Here, the interaction of millimetre-sized gas-encapsulated drops with impulsive laser-induced shock waves is investigated to gain fundamental insights into the release process. Experimental synchrotron X-ray phase contrast imaging, which allows the drop dynamics to be visualised inside the encapsulating bubble, is complemented by numerical simulations to study the intricate physics at play. Three drop dynamical release regimes are discovered, namely the drop impact, partial deposition and jet impact regimes. The regime type is mainly dependent on the shape of the bubble interface impacting the drop and the associated Weber and Reynolds numbers. The drop dynamics of the drop impact and partial deposition regimes show similarities with the canonical configuration of drops impacting flat liquid surfaces, whereas the jet impact regime resembles binary drop collisions, which allows existing scaling laws to be applied to describe the underlying processes. The release of the drop is investigated numerically. The time evolution of the drop dissemination within the surrounding liquid discloses enhanced mixing for dynamics involving high Weber and Reynolds numbers such as the drop impact and jet impact regimes.

  • Quality assessment for large-aperture optical elements inducing phase jumps

  • Vicenţiu Iancu, Anda-Maria Talpoşi, Cristina Gheorghiu, Răzvan Ungureanu, Ioan Dăncuş, Dan-Gheorghiţă Matei, Daniel Ursescu
  • Journal:
    High Power Laser Science and Engineering / Volume 12 / 2024
    Published online by Cambridge University Press:
    19 December 2024, e81
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  • Achieving complex pulses with high-power lasers necessitates rigorous testing of specially designed optical components. The qualification of these components using complementary devices to access both the high-resolution and the large-aperture properties, followed by validation using propagation simulations, is proposed here. In particular, the topology of a large-aperture staircase-like Fresnel phase plate used to generate vortex pulses is qualified using a non-contact optical profiler and a large-aperture wavefront measurement setup based on a Shack–Hartmann sensor. The resulting topography is further used for simulating the focus of laser beams after passing through the phase plate. Step height distribution effects on the doughnut-shaped focus are identified, and avoiding the indicated pitfall in the design of the phase plate provides at least a 10-fold reduction of the irradiance modulation on the circumference of the focus in the super-Gaussian case.

  • Development of a multifunctional optical diagnostic system at the Shenguang-II upgrade laser facility

  • Xinyan Li, Peng Yuan, Fan Gao, Yifan Liu, Lixuan Wu, Xiaohui Yuan, Zhe Zhang, Jie Zhang, Jun Li, Jian Zheng
  • Journal:
    High Power Laser Science and Engineering / Volume 12 / 2024
    Published online by Cambridge University Press:
    19 December 2024, e78
    • Article
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  • A multifunctional optical diagnostic system, which includes an interferometer, a refractometer and a multi-frame shadowgraph, has been developed at the Shenguang-II upgrade laser facility to characterize underdense plasmas in experiments of the double-cone ignition scheme of inertial confinement fusion. The system employs a 266 nm laser as the probe to minimize the refraction effect and allows for flexible switching among three modes of the interferometer, refractometer and multi-frame shadowgraph. The multifunctional module comprises a pair of beam splitters that attenuate the laser, shield stray light and configure the multi-frame and interferometric modules. By adjusting the distance and angle between the beam splitters, the system can be easily adjusted and switched between the modes. Diagnostic results demonstrate that the interferometer can reconstruct electron density below 1019 cm–3, while the refractometer can diagnose density approximately up to 1020 cm–3. The multi-frame shadowgraph is used to qualitatively characterize the temporal evolution of plasmas in the cases in which the interferometer and refractometer become ineffective.

  • 12 - Direction, strength, and shape of incident shock waves

  • from Part 2 - Hydrodynamics of Complex Flows
  • Ye Zhou, Lawrence Livermore National Laboratory, California
  • Book:
    Hydrodynamic Instabilities and Turbulence
    Published online:
    27 June 2024
    Print publication:
    19 December 2024, pp 230-246

  • Summary

    Unlike RT instabilities, where the instability can grow only when light fluids push into heavy fluids, RM instabilities can develop both when shockwaves travel from light fluids to heavy fluids and vice versa. We will also discuss the physics associated with the "shock proximity" and introduce nonstandard RM flows.

Page 215 of 11903